A wake-up call means a warning that makes someone realize action is needed. This answer is correct because the expression has a fixed figurative meaning in English. In an SSC idiom question, students should match the whole phrase with its accepted meaning rather than translate each word separately.

• Classroom example: A wake-up call can refer to a warning that makes someone realize action is needed.
• Story example: A writer may use A wake-up call when describing a warning that makes someone realize action is needed.
• Exam example: When a sentence contains A wake-up call, choose the meaning “a warning that makes someone realize action is needed.”